Molded articles are useful in a variety of applications. Molded articles include both thermoset composite and thermoplastic material. Thermoset composite materials are made by combining a fiber reinforcement with a liquid resin. The resin wets the fiber reinforcement material and then cures. Thermoplastic material is thermoformable and may be injection molded or blow-molded to form articles having very complex shapes. Blow-molding is especially useful for manufacturing articles for holding fluids such as containers.
Both types of molded articles are generally sensitive to exposure at elevated temperatures. Thermoplastic and thermoset composite articles tend to soften when exposed to temperatures above their melting point. Thermoset composite articles tend to oxidize the resin portion of the composite material. In both cases, the molded article becomes structurally weakened by the exposure to elevated temperatures. When localized areas are exposed to elevated temperature, these localized areas tend to weaken.
A variety of methods have been used to protect a molded article from exposure to high temperatures. Various types of heat shields have been affixed either to the elevated temperature source or the molded article. These heat shielding devices include various layers of perforated metal sheets containing spaces or baffles to insulate the molded article from high temperatures. Problems with add-on heat shields of this type include the added bulk and cost of incorporating add-on heat shields to molded articles. In some applications, the weight saved between a molded article and a steel article has been more than made up by the requirement for add-on heat shields.
Another method of protecting molded articles from elevated temperatures is the use of high temperature resistant resins and thermoplastic materials. These new materials may permit molded articles to withstand elevated temperatures without need of add-on heat shields. The disadvantage of these new high temperature resistant materials is they are not capable of withstanding very high temperatures in excess of 1000.degree. F. Their cost and the difficulty in processing these materials do not make them commercially feasible in large production situations.
In many applications, the exposure of the molded article to elevated temperature is localized. Manufacturing an entire molded article with these high temperature resistant materials is unnecessary. It is one object of the present invention to provide an integral heat shield for protecting localized areas of molded articles from elevated temperatures. It is a further object of the present invention to provide a low cost method of fabricating a molded article with an integral heat shield. It is a further object of the present invention to provide a lightweight molded article having and integral heat shield to protect localized areas from elevated temperatures.